I cannot post to the development section, so I post here. Maybe someone can forward to that section.

I have used v0.3.21 windows and it has option "Generate coin". but today when I download and install v.0.3.23, the "generate coin" option is missing.

How do I generate coin with the original client?

Thanks.

You don't, you've been wasting electricity. If you want to generate a block using the bitcoin client, it would take you something like 600 years to find one. Download a proper GPU mining client, or at least a CPU one. Locked.